# 原数据
"""

A 	B 	C 	D
a 	b1 	c 	2001
a 	b1 	c 	2003
a 	b1 	c 	2005
a 	b2 	c 	2001
a 	b2 	c 	2002
a 	b2 	c 	2003
a 	b2 	c 	2004
"""


